1. Field of the Invention
This invention relates generally to a magnetic recording and/or reproducing apparatus, such as, a video tape recorder or VTR, and more particularly is directed to improving the recording of audio in such apparatus of the type in which luminance and chrominance signals comprising a color video signal are recorded in separate tracks.
2. Description of the Prior Art
Color television or video signals according to the NTSC standard include a luminance signal and a chrominance signal comprised of components quadrature-modulated on a color subcarrier. When it is desired to record such an NTSC color video signal in a VTR, it is found that the total band width of the NTSC signal is so large that side bands of the frequency-modulated carrier extend over a greater frequency band than that which can be accommodated within the FM channel of the VTR. Consequently, the so-called "color under" system has been used in which the color subcarrier, quadrature-modulated with the chrominance signal components, is directly recorded at a relatively low frequency in the same track with an FM carrier modulated by the luminance signal. While the "color under" system allows recording of a color video signal on a single track of a magnetic tape in a VTR, certain problems are associated therewith, such as, poor signal/noise ratio in respect to the chrominance signal, cross-talk between the two quadrature-modulated chrominance signal components, and a limited frequency band width. Further, the FM luminance carrier cannot be modulated to its fullest extent because of possible saturation of the recording medium leading to distortion of the directly recorded chrominance signal. Further, many existing VTRs are burdened by relatively low fidelity reproduction of the audio signals associated with the recorded color video signal. In such VTRs, audio signals are recorded and reproduced by fixed magnetic heads in tracks extending longitudinally along the magnetic tape, while the color video signal is recorded by rotary heads in tracks extending obliquely across the tape. Due to the relatively slow speed of movement of the tape in the longitudinal direction during recording and reproducing operations, the audio signals recorded and reproduced by fixed heads are inherently of relatively poor quality, and such poor quality is only marginally improved by frequency modulating the audio signal for the recording thereof.
In order to improve the quality of the recorded audio signal, it has been proposed, for example, as disclosed in detail in U.S. Pat. No. 4,490,751, having a common assignee herewith, to provide a video and audio signal recording apparatus in which a first audio signal, for example, a stereophonic left-channel signal, frequency modulates first and second carriers, thereby providing first and second FM audio signals, respectively, while third and fourth carriers are frequency modulated by a second audio signal, for example, a stereophonic right-channel signal, for providing third and fourth FM audio signals, respectively, with such first to fourth carriers all having different respective frequencies. Two of the FM audio signals which represent the first and second audio signals to be recorded, respectively, are mixed with a video signal for providing a first mixed audio and video signal, and the other two FM audio signals are mixed with the video signal to provide a second mixed audio and video signal, whereupon, first and second magnetic heads having different azimuth angles receive the first and second mixed audio and video signals for recording such first and second mixed signals in respective record tracks which are adjacent each other on the magnetic tape. In a preferred arrangement of the foregoing video and audio signal recording apparatus, when the video signal to be recorded is a color video signal including a luminance signal and chrominance signal components, the luminance signal frequency modulates an additional carrier having a frequency higher than that of all the carriers of the FM audio signals so that the resulting FM luminance signal is in a band above the band containing the first through fourth FM audio signals, and the chrominance signal is frequency converted to a relatively low frequency band spaced from the band of the FM luminance signal for providing a gap therebetween in which all of the FM audio signals are situated. Since, in this arrangement, the FM audio signals are recorded and reproduced by the rotary heads in the oblique tracks on the magnetic tape, a high head-to-tape speed is attained and the quality of the recorded and reproduced audio signals is improved. However, since the chrominance and luminance signals of the color video signal are recorded in the same track, the previously mentioned problems associated with such arrangement are still encountered, and are even accentuated by the fact that the band widths available for recording the luminance and chrominance signals are further limited by the need to provide a gap therebetween for accommodating the FM audio signals.
In order to improve the quality of the recorded and reproduced color video signal, it has been proposed, for example, in U.S. Pat. No. 4,376,957, issued Mar. 15, 1983, and in U.S. Pat. No. 4,580,173, issued Apr. 1, 1986, to provide a VTR for recording a color video signal comprised of a luminance signal and a chrominance signal constituted by at least two chrominance signal components, and in which the luminance and chrominance signals are recorded by respective rotary heads in alternate slant tracks, respectively, extending obliquely across the magnetic tape, with the chrominance signal components being time-base-compressed and time-division-multiplexed so as to be arranged alternately in sequence in the respective tracks. By thus recording the luminance and chrominance signals in separate tracks, the quality of the recorded and reproduced color video signal is substantially enhanced. However, in existing proposals for recording the luminance and chrominance signals in separate slant tracks, the audio signals are still recorded in tracks extending longitudinally along the magnetic tape by means of fixed heads so that the head-to-tape speed is very low with the result that the reproduced audio signals are of poor quality which is not sufficiently improved by recording frequency modulated audio signals.